The present invention relates to the art of color proofing, and in particular, to an improved lamination assembly and roller for preparing prepress color proofs, such as by the use of pressure and heat to laminate media together. It should be known that this invention could be used in any field that uses rollers or belts to convey or fuse media.
Pre-press color proofing is a procedure used by the printing industry to create representative images of printed material. The proof is used to check for color balance and other important image quality control parameters, without the high cost and time that would be required to actually produce printing plates set up a printing press to produce an example of an intended image. The pre-press color proof of the intended image may require several corrections and may be reproduced several times to satisfy or meet the requirements of the customers, resulting in a large loss of profits and ultimately higher costs to the customer.
Color proofs sometimes called xe2x80x9coff pressxe2x80x9d proofs or prepress proofs, are one of three types. The first is a color overlay that employs an image on a separate base for each color. The second a single integral sheet process in which the separate color images are transferred by lamination onto a single base. The third is a digital method in which the images are produced directly onto or transferred by lamination onto a single base from digital data.
In one typical process for a prepress color proofing system used in the printing industry, a multicolor original is separated into individual transparencies, called color separations, the three subtractive primaries and black. Typically a color scanner is used to create the color separations and in some instances more than the four standard color separations are used. The color separations are then used to create a color proof that is sometimes called an xe2x80x9coff pressxe2x80x9d proof or prepress proof as described above.
In one type of laminator, noted in a copending patent application cited above, a lamination sandwich sits on an entrance table. A leading edge of the lamination sandwich is fed into the laminator. An upper pressure roller and a lower pressure roller receive this lamination sandwich. The lamination sandwich passes completely between the upper heated pressure roller and a lower heated pressure roller coming to rest on an exit table. With the configuration of an upper heated pressure roller and a lower heated pressure roller as described above, the laminator is termed a straight-through laminator. As an additional reference U.S. Pat. No. 5,203,942 describes a lamination/de-lamination system as applied to a drum laminator.
While the above-described laminator works well for some materials and in limited conditions, there are many conditions and materials that cannot be laminated successfully using the above-described laminator. One problem is the intended image shifting from one color to another such that the dots/image from one color to the next are not overlaid correctly causing a misregistration of the intended image. The intended image may suffer from overall image growth and damage to some intended images may occur in the form of creases commonly know as rivers or valleys.
The aforementioned problems are for the most part due to the heated pressure rollers and the application thereof. The upper heated pressure roller and the lower heated pressure roller have hollow heater elements that are typically made of metal. The hollow portion of the heater element is for accepting a heating rod or lamp while a rubber layer or shell typically of silicone rubber is formed around the outside of the heater element. When the upper heated pressure roller and the lower heated pressure roller are pressed together, they form a nip or indentation. Within the nip formed by the upper heated pressure roller and the lower heated pressure roller, lateral shear stresses and overdrive conditions are formed. These lateral sheer stresses and overdrive conditions act upon the media being laminated together to cause the intended image to shift from one color to another color. These lateral sheer stresses and overdrive conditions can also cause a defect in the final lamination in the form of creases commonly known as rivers or a valley, as described above. These lateral sheer stresses and overdrive conditions can also cause image growth which can be different with each color, causing the intended image to be misregistered from one color to the next color or to be larger than the original image or printed image. Although adding a deformable layer as described in U.S. patent application Ser. No. 09/676,877 helps to eliminate the above mentioned problems there is still room for improvement.
An object of the present invention is to provide for an apparatus and method that overcome the drawbacks noted above.
The invention relates to a laminator assembly comprising: a first roller located on a first side of a media passage; a second roller located on a second side of said media passage so as to oppose said first roller, wherein a nip portion is defined between said first and second rollers so as to apply pressure to media in said media passage which passes through said nip portion; and wherein at least one of said first and second rollers is a roller comprising a substantially solid layer which may be solid. Surrounding this substantially solid layer is a deformable layer. Surrounding the substantially solid layer is a perforated layer which in alternative embodiments can be a solid layer upon which have disposed a coating, leaving a portion of the solid layer uncoated. These uncoated portions can be in the shape of arcs, curves, or circles or any one of a number of shapes. Alternatively, the perforations on this layer may be in the form of a shapes as well. One or more of the rollers can be heated or adapted to accept a heating element.
The present invention provides for a roller arrangement that overcomes lateral shear stresses and overdrive conditions, and allows the use of low durometer rubber or of a compressible rubber, and can be used in laminators or any number of devices, including copiers and fax machines.
The present invention further provides for a heated pressure roller embodiment that allows a wider range of conditions for lamination.
The present invention further provides for a pressure roller that allows a wider range of conditions for conveying media.
The present invention also provides for a roller arrangement that helps overcome image shift from one color to another and overall image growth. Additionally, the present invention provides for a heated pressure roller that improves defects such as creases/rivers or valleys.
According to a feature of the present invention, a laminating system for bonding, to a paper receiver stock, a thermal print media of the type including a carrier and a material to be applied to the paper receiver stock, includes an improved pair of pressure rollers, which can be heated. Through these rollers, media or a lamination sandwich of thermal print media and paper receiving stock can be fed. The pair of rollers having been improved by adding, to at least one of the pressure rollers, a metal or plastic perforated belt or tube over a rubber or otherwise deformable material layer of the heated roller. This coating serves to prevent lateral stresses, overdrive conditions from acting on the thermal print media or paper receiving stock or allow the media to slip.
The present invention relates to a drive roller assembly for conveying media, which is comprised of opposing rollers. The rollers of this assembly, which optionally can comprise a heater element, consist of a first deformable layer, a second perforated layer which surrounds the first de-formable layer and forms an outer surface of one of the first and second opposing rollers or both.
The present invention relates to a belt for conveying media, which is comprised of a de-formable layer and a perforated layer or covering.
The invention, and its objects and advantages, will become more apparent in the detailed description of the preferred embodiments presented below.